Is the fabled city of Timbuktu about to be rescued? Two weeks after France began bombing Islamic militant positions in northern Mali, columns of French and African armored vehicles snaking northward through the country are closing in on the ancient capital of the old Malian Empire, which has been ruled under harsh Shari‘a by militant Islamists since last spring.

That might seem like good news. But as the troops advance, the anxiety has risen among those who’ve spent years and millions of dollars trying to preserve the city’s centuries-old history. The fear, they say, is that if there is ground combat, once the forces arrive in Timbuktu, it could be as perilous to cultural treasures as the Islamists’ nine-month occupation. “Wherever you see military intervention, things are bound to get destroyed,” says Shamil Jeppie, director of the Timbuktu Manuscripts Project at the University of Cape Town, which has worked with the South African government to preserve thousands of old documents. “My initial fear was of neglect,” he says. “The fear now is outright war and military engagement.”

On Friday, there were reports that rebels had fled Timbuktu after France bombed a militant base set in a building once owned by Libya’s Muammar Gaddafi. By Saturday night, correspondents traveling in the country tweeted that Timbuktu’s mayor, who fled last year, was looking for a ride back home the following day. What he finds could be grim. Earlier this week, Agence France-Presse reported that the rebels had left Timbuktu without water or electricity. “It’s a ghost town,” Moctar Ould Kery, a local official, told AFP on Friday. In interviews, Timbuktu residents who are currently living in Bamako or abroad said telephones appeared to have gone dead around Tuesday. All that is small comfort to the preservationists, who say they will not rest easy until French and African forces arrive in Timbuktu.

At stake are about 300,000 manuscripts stashed around northern Mali, whose residents, many of them nomadic ethnic Tuareg, have been custodians of Timbuktu’s old literary tradition, dating back to the time of the Renaissance, when the city was a major crossroads for gold traders. Bound in weathered goatskin covers, they have survived countless perils along the way. Indeed, many of the manuscripts detail the region’s tumultuous history. Since 2009, about 40,000 of them have been housed in a modern adobe building called the Ahmed Baba Institute, partly financed by the South African government; militants are believed to have occupied the building since they seized control of Timbuktu last March, and Jeppie said its computers and vehicles had been stolen.

When TIME visited Timbuktu in 2009 to report about the documents, many were piled in rickety closets with little security, often in people’s living rooms, passed from generation to generation over centuries. Several residents explained how priceless family collections, some carried during the 15th century when their ancestors fled southern Spain, were regularly hidden deep in the desert during times of conflict, and then dug out again during peacetime.

So far, the documents have remained safe, this time around too. Yet preservationists are nervous, fearing that any focus on their historical value could provoke militants to attack them. Preservationists cite the destruction last June by members of the al-Qaeda-linked group, Ansar Dine, who smashed Sufi shrines in Timbuktu, some of them 500 years old. Just days before, the U.N.’s cultural organization, UNESCO, had placed Timbuktu on its list of endangered sites, saying it feared that criminal gangs would take advantage of Mali’s upheaval to try to sell historic items on the black market, or that rebels could target sites or objects out of vengeance or religious fervor. Ansar Dine’s spokesman Sanda Ould Boumama told AFP at the time that they had acted “in the name of God,” because the mausoleums were deemed offensive to Islam.

As the city of 55,000 fell to the rebels last March, those who fled hand-carried manuscripts out of the city and locked others away in safe houses. Set in the remote Sahara on a bend of the Niger River, Timbuktu, which is 1,000 miles (1,600 km) from Mali’s capital, Bamako, has, in truth, had far more urgent issues to cope with than its cultural heritage, including deep poverty and a dire lack of resources. During the past nine months, thousands have fled south, escaping the Islamist rule, in which self-appointed Shari‘a judges have carried out amputations, banned music and forced women off the streets.

Still, residents have reportedly rallied during the occupation to shelter their treasures. “We’ve spared no effort to take the manuscripts away from any risk of damage, which is why we’ve moved them to discreet, secure locations,” says Banzouman Traoré, who has catalogued thousands of documents for Savama, an association of Timbuktu’s 30 or so family-owned historic libraries. “To our knowledge, no manuscripts have suffered damage, but we believe there is a potential risk if we do nothing,” he told TIME by phone from Bamako.

Fearing that the libraries could accidentally be hit in a bombing raid, UNESCO last month printed the GPS coordinates of where they were and distributed 3,000 copies to French and African military forces, says Bandiougou Diawara, a Malian working on Timbuktu’s heritage for UNESCO. He says that in recent weeks, the organization has also printed about 8,000 copies of a “passport of cultural heritage” for police and humanitarian groups in Mali, with photos of protected historic objects, in case militants seize them as they flee the advancing French-African forces, or to stop residents from trying to sell them on the black market. So nervous, in fact, are conservationists about Timbuktu, that most have been loath to discuss their concerns publicly, for fear that it would tip off the Islamists. The documents, Malians believe, are living proof of the continent’s long intellectual history; uncovered by Western explorers during the 1970s, the manuscripts’ sophisticated astronomical maps and mathematical theory have astonished scholars.

An international effort began in the 2000s to try to save the documents from disintegration. That is by no means easy. Since the paper and inks are too fragile to withstand scanning, each page has to be photographed. When the rebels entered Timbuktu last March, only about 10% of the documents had been digitized. The preservationists hope they will soon be back at work.